Abstract: Gulf Coast Cenozoic Sediments and Structure: An Excellent Example of Extra-Continental Sedimentation

By

Donald P. McGookey

Relatively abrupt stratigraphic and structural changes reflect the transition from continental to oceanic crust in the northern Gulf of Mexico basin. This transition is coincident with the hinge zone where the thick Cenozoic clastic section progrades basinward from Mesozoic carbonate shelves. Cenozoic sediments were poured at high rates into areas underlain by mobile deep water muds and Jurassic salt. Loading on an unstable section combined with subsidence of the oceanic crust caused by loading, developed a complex interrelation of structural and sedimentation events that progressed in two phases. Initially, sedimentation at or near the shelf edge caused the underlying shale and/or salt to flow into a series of ridges. Intervening areas became depopods which were self-perpetuating as sediment dumping grounds until up to 14 km was accumulated. At that point near isostatic equilibrium was reached, and the delta front or shelf edge prograded farther basinward to repeat phase one in that area. During phase two basin-wide loading caused slow regional subsidence that allowed deposition of an additional 3 km of nearly horizontal sediments. This section is undisturbed except for local salt piercements.

These relationships may be present worldwide where deltaic progradation causes significant loading of oceanic crust. Conversely, the recognition along the edge of a continent of thick sedimentary sections (17 km) with the structural-depositional relations described, signifies sedimentation on oceanic crust.

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